Certain medicaments for parenteral use cannot be stably stored over extended periods of time in the liquid phase. For example, an extended period of time is to be understood to include a time interval of at least eighteen months during which the medicals are to be stored at a temperature of typically 2° C.-8° C. Such medicaments which cannot be stably stored over extended periods of time in the liquid phase are typically stored in form of a solid product comprising one or more active pharmaceutical ingredients (APIs). An active pharmaceutical ingredient is a substance in a formulation that is biologically active. For example, the active pharmaceutical ingredient causes the direct effect on the disease diagnosis, prevention, treatment or cure. A product comprises one or more active pharmaceutical ingredients (APIs) that may be for example one or more proteins, antibodies, small molecules, etc. A product may, in addition to the one or more active pharmaceutical ingredients (APIs), comprise additional non-active pharmaceutical ingredients commonly called excipients. As has been discussed above already, the liquid product may be dried to form a solid product comprising the one or more active pharmaceutical ingredient(s) (API) with or without excipients. Drying of the liquid product can be achieved by lyophilisation (freeze drying) or spray drying or any other drying method. This aspect is particularly advantageous since drying of a product comprising an API, in particular freeze drying of a product comprising an API, is a gentle process of producing a solid product comprising the API, so that the dried solid product can be stably stored separate from a liquid solvent over extended periods of time. The so obtained solid product can be stably stored, for example, in vials, syringes, cartridges or in one chamber of a dual chamber syringe/dual chamber cartridge. To reconstitute the medicament for parenteral use the solid product is solved in a liquid diluent. For example, the liquid solvent may be water for injection, saline, bacteriostatic water for injection (containing one or more preservative) or any other suitable liquid solvent (diluent).
By way of example, the syringe head of a dual chamber syringe/cartridge can be formed like a vial (i.e. a cartridge), can be formed containing a luer cone or luer slip, or can comprise a cone including a needle (staked in needle syringe). For dual chamber syringes/dual chamber cartridges a separating middle plunger is arranged between the two chambers in the syringe barrel in a sealing position in which the plunger seals the two chambers from each other. By applying pressure to a plunger rod attached to an end plunger of the dual chamber syringe/dual chamber cartridge, the end plunger is moved in a direction towards the syringe/cartridge head and applies pressure to the liquid solvent which causes the middle plunger to move from its sealing position into a bypass position in which the liquid solvent is allowed to flow into the chamber containing the solid product comprising the API. The medicament to be administered is then getting reconstituted for the subsequent administration to a patient, the administration being performed by further moving the plungers towards the syringe/cartridge head.
In the processing of dual chamber syringes/cartridges containing the dried solid product and the liquid solvent separated from each other, the separating middle plunger is typically inserted into its sealing position, before filling the liquid product containing the API through the syringe/cartridge head (limiting the syringe head to a design suitable for filling through the syringe head). The syringe barrel is then transferred into a drying chamber where the drying is formed through forced water evaporation or sublimation of the liquid product.
The time required for drying the liquid product containing the API is greatly influenced by the thermal conductivity of the material the dual chamber syringe is made of. Typically, primary packaging containers such as vials, cartridges, syringes and dual chamber syringes are made of glass or plastic materials, with all types of materials having only a poor thermal conductivity. As a consequence thereof, comparatively long time intervals are necessary to complete the drying of the liquid product containing the API in order to obtain the dried solid product. In addition, the two chambers of a dual chamber syringe/cartridge are arranged in sequence along the longitudinal extension of the syringe, thus resulting in a considerable length of the dual chamber syringe/cartridge, while the liquid product containing the API is arranged only in one of these chambers. Accordingly, while the dual chamber syringes/cartridges occupy a considerable amount of space of the drying chamber, only a small amount of the occupied space is actually utilized for drying, since the liquid product to be dried is arranged only in one chamber of the dual chamber syringe/cartridge. As a consequence, the drying chamber is inefficiently used both in terms of the time necessary to complete drying and in terms of space occupied by the dual chamber syringes/dual chamber cartridges. It is evident, that such inefficient use of the drying chamber influences the efficiency of the entire production process which is therefore open to improvement.